Although screening, brief intervention, and referral to treatment (SBIRT) approaches are effective in reducing alcohol misuse and its associated risk-taking behaviors and negative consequences, there is little research demonstrating the effectiveness of SBIRT for illicit and/or prescription drug misuse. Misusers of illicit and/or prescription drugs frequently seek medical care in emergency departments (EDs), particularly for reasons related to their misuse. As a result, the ED is well suited as a site to conduct an analysis of the effectiveness of SBIRT for this population. The Brief Intervention for Drug Misuse for the Emergency Department (BIDMED) study is a randomized, controlled, trial that will include adult ED patients at a large, academic, trauma center (Rhode Island Hospital) and a community hospital (The Miriam Hospital) who have a subcritical illness or injury and whose screening indicates illicit and/or prescription drug misuse. BIDMED participants will be randomized to receive screening only (SO) or brief intervention (BI) with appropriate referral to treatment. Participants will complete a battery of blinded baseline assessments using standardized instruments as well as adapted instruments specific to the aims of this study. All participants will undergo blinded follow-up assessments at three, six, and twelve months post-randomization. The primary hypotheses addressed in the BIDMED study are that, compared to participants in the SO arm, participants in the BI arm will show a significantly greater reduction in: (1) drug misuse within the prior 30 days at three months post-randomization, (2) behaviors associated with drug misuse at six months post-randomization; and (3) negative physical health, psychosocial health, and socioeconomic consequences at twelve months post-randomization. As a secondary aim, the impact of BI compared to SO will be assessed on participants contacting, enrolling in, and completing a drug treatment program. In addition, the impact of BI compared to SO on increasing uptake of HIV and hepatitis B/C screening will be measured. A mechanisms of change model that addresses the expected mediators and moderators of change to explain the effects of SBIRT in this setting will also be developed and tested. Further, the epidemiology of illicit and/or prescription drug misuse will be assessed in a random sample of ED patients.